In most contemporary high speed printers a carriage mounts a printing head, often of the wire matrix type, and printing occurs as the carriage is moved across a line of a document. Existing printers print on the fly and each time a line of print is completed, the carriage returns to the customary left margin or home position. Generally, sensors are located at the left margin and right margin positions so that the end of a line is sensed which causes the return of the carriage to the left margin or home position. Such a prior art mechanism is disclosed in U.S. Pat. No. 3,882,988 to Sloan et al.
In the printing of certain forms, it is customary for information to be printed on the right or left portion of a document, with respect to a center line through the document, instead of a complete line across the width of the document. If a number of different lines are to be printed this way, a loss of time would be incurred when the carriage travels the entire distance between the left margin and right margin. Accordingly, it would be of great advantage if a mechanism could be installed on high speed printers which would sense the center location and begin a print operation relative to the center location. As an example of the utility for the present invention, reference is made to customary car rental forms which generally have information printed across an entire line of the form on certain portions of the document while on other portions of the document line after line is printed between the document center and the margins. In repetitive printing operations of car rental forms for waiting customers, the increased speed of document completion is advantageous. Of course, the utilization of the present invention in connection with car rental forms is merely illustrative and pertains to the printing of forms and documents, generally.